Semiconductor light-emitting devices including light emitting diodes (LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavity laser diodes (VCSELs), and edge emitting lasers are among the most efficient light sources currently available. Materials systems currently of interest in the manufacture of high-brightness light emitting devices capable of operation across the visible spectrum include Group III-V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III-nitride materials. Typically, III-nitride light emitting devices are fabricated by epitaxially growing a stack of semiconductor layers of different compositions and dopant concentrations on a sapphire, silicon carbide, III-nitride, or other suitable substrate by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. The stack often includes one or more n-type layers doped with, for example, Si, formed over the substrate, one or more light emitting layers in an active region formed over the n-type layer or layers, and one or more p-type layers doped with, for example, Mg, formed over the active region. Electrical contacts are formed on the n- and p-type regions.
FIGS. 1A, 1B, 1C, and 1D illustrate a method of forming a phosphor-converted LED, described in more detail in US 2013/0187174. In FIG. 1A, a base 410 is provided and light emitting elements (LEEs) 210 are placed on or adhered to base 410 with contacts 220 adjacent to base 410. The LEEs 210 have a spacing 405 between adjacent elements. Base 410 may also be referred to as a “mold substrate.” In one embodiment, base 410 includes or consists essentially of an adhesive film or tape. In some embodiments, base 410 includes or consists essentially of a material to which has a relatively low adhesion to phosphor 230, that is, it permits removal of cured phosphor 230 from base 410.
In FIG. 1B, barriers 450 are formed. Barriers 450 are shown as perpendicular or substantially perpendicular to a surface 435. The spacing 405 between adjacent LEEs 210 may be adjusted to control the width of cured phosphor 230 around the sides of LEEs 210 as shown in FIG. 1D. Spacing 405 between LEEs 210 is approximately determined by the sum of twice the desired sidewall thickness of the phosphor and the kerf (where the kerf is the width of the region removed during the singulation process of finished dies 200, for example identified as kerf 470 in FIG. 1D. The thickness of cured phosphor 230 over the LEEs 210 may be controlled by controlling a thickness 425 of phosphor 420 that is formed or dispensed as shown in FIG. 1B. Thickness 260 of cured phosphor 230 over LEE 210 is given approximately by the thickness of dispensed phosphor, 425 less the thickness 445 of the LEE. Phosphor 420 includes or consists essentially of a phosphor and a binder. Phosphor 420 is contained or bounded by surface 435 of base 410 and optional sides or barriers 450. Phosphor 420 has a bottom surface or face 460 and a top surface or face 440, which are substantially parallel to each other.
Phosphor 420 is then cured, producing cured phosphor 230 as shown in FIG. 1C.
In FIG. 1D, white dies 200 are separated or singulated from the structure shown in FIG. 1D. White dies 200 may have a size ranging from about 0.25 mm to about 5 mm.